1. 以C结构体或C++的“类”代替“第2章中复杂数据类型”，实现“链式线性表”，编写下面6个接口函数：CreateList、ListPrint、GetElem、ListLength、ListInsert、ListDelete

1. C结构体实现链式线性表

#include <stdio.h>
#include <stdlib.h>

typedef struct ListNode {
    int data;
    struct ListNode* next;
} ListNode;

typedef struct LinkedList {
    ListNode* head;
    int length;
} LinkedList;

2. CreateList

LinkedList* CreateList() {
    LinkedList* L = (LinkedList*)malloc(sizeof(LinkedList));
    L->head = NULL;
    L->length = 0;
    return L;
}

3. ListPrint

void ListPrint(LinkedList* L) {
    ListNode* p = L->head;
    while (p != NULL) {
        printf("%d ", p->data);
        p = p->next;
    }
    printf("\n");
}

4. GetElem

int GetElem(LinkedList* L, int index) {
    if (index < 1 || index > L->length) {
        printf("Error: Index out of range.\n");
        return -1;
    }
    ListNode* p = L->head;
    int i = 1;
    while (i < index) {
        p = p->next;
        i++;
    }
    return p->data;
}

5. ListLength

int ListLength(LinkedList* L) {
    return L->length;
}

6. ListInsert

void ListInsert(LinkedList* L, int index, int value) {
    if (index < 1 || index > L->length + 1) {
        printf("Error: Index out of range.\n");
        return;
    }
    ListNode* newNode = (ListNode*)malloc(sizeof(ListNode));
    newNode->data = value;
    newNode->next = NULL;
    if (index == 1) {
        newNode->next = L->head;
        L->head = newNode;
    } else {
        ListNode* p = L->head;
        int i = 1;
        while (i < index - 1) {
            p = p->next;
            i++;
        }
        newNode->next = p->next;
        p->next = newNode;
    }
    L->length++;
}

7. ListDelete

void ListDelete(LinkedList* L, int index) {
    if (index < 1 || index > L->length) {
        printf("Error: Index out of range.\n");
        return;
    }
    if (index == 1) {
        ListNode* p = L->head;
        L->head = L->head->next;
        free(p);
    } else {
        ListNode* p = L->head;
        int i = 1;
        while (i < index - 1) {
            p = p->next;
            i++;
        }
        ListNode* q = p->next;
        p->next = q->next;
        free(q);
    }
    L->length--;
}

完整代码：

#include <stdio.h>
#include <stdlib.h>

typedef struct ListNode {
    int data;
    struct ListNode* next;
} ListNode;

typedef struct LinkedList {
    ListNode* head;
    int length;
} LinkedList;

LinkedList* CreateList() {
    LinkedList* L = (LinkedList*)malloc(sizeof(LinkedList));
    L->head = NULL;
    L->length = 0;
    return L;
}

void ListPrint(LinkedList* L) {
    ListNode* p = L->head;
    while (p != NULL) {
        printf("%d ", p->data);
        p = p->next;
    }
    printf("\n");
}

int GetElem(LinkedList* L, int index) {
    if (index < 1 || index > L->length) {
        printf("Error: Index out of range.\n");
        return -1;
    }
    ListNode* p = L->head;
    int i = 1;
    while (i < index) {
        p = p->next;
        i++;
    }
    return p->data;
}

int ListLength(LinkedList* L) {
    return L->length;
}

void ListInsert(LinkedList* L, int index, int value) {
    if (index < 1 || index > L->length + 1) {
        printf("Error: Index out of range.\n");
        return;
    }
    ListNode* newNode = (ListNode*)malloc(sizeof(ListNode));
    newNode->data = value;
    newNode->next = NULL;
    if (index == 1) {
        newNode->next = L->head;
        L->head = newNode;
    } else {
        ListNode* p = L->head;
        int i = 1;
        while (i < index - 1) {
            p = p->next;
            i++;
        }
        newNode->next = p->next;
        p->next = newNode;
    }
    L->length++;
}

void ListDelete(LinkedList* L, int index) {
    if (index < 1 || index > L->length) {
        printf("Error: Index out of range.\n");
        return;
    }
    if (index == 1) {
        ListNode* p = L->head;
        L->head = L->head->next;
        free(p);
    } else {
        ListNode* p = L->head;
        int i = 1;
        while (i < index - 1) {
            p = p->next;
            i++;
        }
        ListNode* q = p->next;
        p->next = q->next;
        free(q);
    }
    L->length--;
}

int main() {
    LinkedList* L = CreateList();
    ListInsert(L, 1, 1);
    ListInsert(L, 2, 2);
    ListInsert(L, 3, 3);
    ListInsert(L, 4, 4);
    ListInsert(L, 5, 5);
    printf("List: ");
    ListPrint(L);
    printf("Length: %d\n", ListLength(L));
    printf("Element at index 3: %d\n", GetElem(L, 3));
    ListDelete(L, 3);
    printf("After deleting element at index 3: ");
    ListPrint(L);
    printf("Length: %d\n", ListLength(L));
    return 0;
}